He was elected to the episcopacy by the Holy and Sacred Synod of the Ecumenical Patriarchate of Constantinople in 1969, and consecrated as Bishop of Apameia later that year, and appointed to the Diocese (Seventh District) of Detroit as Bishop of that district. He was enthroned by His Eminence ArchbishopIakovos of the Greek Orthodox Archdiocese of North and South America on May 1, 1979, as the Bishop of Chicago at the Annunciation Cathedral. In November 1997, the Holy Synod of the Ecumenical Patriarchate elected His Grace Bishop Iakovos of Chicago to the active Metropolitanate of Chicago and Exarch of Ionias. In this capacity, His Eminence serves the Greek Orthodox Diocese of Chicago as its Presiding Hierarch.

Beginning his higher education in Athens, Greece, and continuing his studies and service in the Boston area, Metropolitan Iakovos was appointed Archdiocesan Vicar of the Diocese of Detroit by Archbishop Iakovos in February 1968. One year later, he was elevated to the rank of Bishop by the Holy See of Constantinople. He was consecrated Bishop of Apameia (an Auxiliary Bishop of Archbishop Iakovos) on Christmas Day of 1969, and appointed to the Diocese of Detroit as Bishop of that district.

In 1971 he was appointed President of Hellenic College and Holy Cross School of Theology in Brookline, Massachusetts, while remaining as administrative overseer of the Diocese of Detroit. He simultaneously served as the Bishop of the New England area during his five-year tenure as President of Hellenic College and Holy Cross School of Theology.

The Diocese of Chicago consists of 34 parishes in Illinois, with another 24 parishes in Wisconsin, Minnesota, Iowa, northern Indiana, and eastern Missouri. The general offices of the Greek Orthodox Diocese of Chicago are located in Chicago, Illinois.

Since assuming the position of Presiding Hierarch of the Diocese of Chicago, Metropolitan Iakovos has characterized his tenure by his many initiatives. Under his leadership the Diocese has increased its efforts to assist the homeless and those in need, as witnessed in the labors of the Diocesan Philanthropy Committee. He has founded new Youth programs, established various local Dialogue Commissions with other faith communities and continues to work with other area Religious leaders in promoting justice and truth in our society.

Various other programs of the Diocese established by Metropolitan Iakovos include the Bishop Iakovos Scholarship Assistance Program, the Bishop's Task Force on AIDS, the Diocese Junior Olympics, the Diocese Dance Festival, as well as numerous programs in religion and Greek education.